Of skin washing agents, the properties of the foams to form in washing therewith and the feeling in use thereof are important points to be preferred by consumers, in addition to the primary function of detergency thereof. In particular, those capable of foaming rapidly, capable of forming fine and creamy foams and capable of giving a moist feeling to skin without dehydrating it after washing therewith not giving any skin pulling feeling tend to be preferred by consumers.
Regarding the problems, various types of surfactants, oily ingredients, polymers or the like are heretofore broadly incorporated in the base of a skin washing agent to thereby favorably improve the feeling of foams and the feeling of skin. However, a skin washing agent with a surfactant having high detergency incorporated therein has some problems in that it roughens skin excessively and, after toweling, it may often give a skin-tightness or skin pulling feeling. In addition, it has another problem in that the moisture may be removed from the skin washed therewith and the moisture content of the skin may be thereby reduced.
As a technique of incorporating a surfactant in the base of a skin washing agent, for example, there is proposed a method of incorporating a polyglycerin monoalkyl ether therein (e.g., see Patent References 1 and 2). However, incorporation of such a polyglycerin monoalkyl ether lowers the elasticity of foams, and is therefore unsatisfactory to users since they could not have a feeling of creamy foams.
Additionally, a washing agent is proposed which comprises a combination of a polyglycerin monoalkyl ether, a fatty acid salt, and an ampholytic surfactant and/or a semipolar surfactant (see Patent Reference 3). The combination could give a refreshed feeling but may give a pulling feeling of the skin, and is insufficient in point of the foaming speed and the quality of foams and is therefore unsatisfactory to users.
On the other hand, as a technique of enhancing the foamability and the quality of foams, there is proposed a method of incorporating a polymer in the base of a skin washing agent. For example, there are known a skin washing agent with a polydimethyldiallylammonium chloride or a dimethyldiallylammonium chloride/acrylamide copolymer incorporated therein (e.g., see Patent Reference 4), a skin washing agent with an acrylic acid/dimethyldiallylammonium chloride/acrylamide terpolymer incorporated therein (e.g., see Patent References 5 and 6).
However, these skin washing agents with such a polymer incorporated therein could not be said still satisfactory in point of the foaming speed, and it is difficult to say that the agents could attain a sufficient effect in point of giving a moist feeling with no pulling feeling of the skin washed with them.                Patent Reference 1: JP 2006-282894A        Patent Reference 2: JP 2006-282895A        Patent Reference 3: JP 2007-146029A        Patent Reference 4: JP 62-4799A        Patent Reference 5: JP 2001-64678A        Patent Reference 6: JP 2003-73257A        